Question

A coil is designed for high Q performance at a rated voltage and a specified frequency. If the frequency is made twice the original and the coil is operated at the same rated voltage, then the Q factor will be affected as ____________

(a) Q is halved

(b) Q remains unchanged

(c) Q is doubled

(d) Q increases or decreases but magnitude cannot be measured

The question was asked in an international level competition.

This interesting question is from Advanced Problems on Magnetically Coupled Circuits topic in section Resonance & Magnetically Coupled Circuit of Network Theory

Answer 1

Correct answer is (c) Q is doubled

Best explanation: ω2L = 2ω1L

∴ Q2 = \(\frac{2ω_1 L}{R}\) = 2Q1

∴ Q is doubled.